A process and an installation to carry out the process such as a burning shaft for cement, limestone, gypsum or the like are known (German Pat. No. 31 932), wherein the shaft interior and the column of material in the shaft interior which completely fills the shaft are subidivided by grate-like divider walls which can be extracted laterally from the shaft walling, forming chambers filled with material lying between grates arranged on top of each other. The combustion gases introduced into the shaft interior under the lowest grate traverse from bottom to top all the chambers, respectively the material in the chambers. When the material present on the lowest grate-like divider wall, such as limestone or the like is sufficiently burnt, the material is discharged by extracting laterally the subdivided lowest divider grate, before the following chamber load is transferred in the burning area to the lowest burning grate after the closing of this grate and subsequently thereto all the chamber loads above it are transported to one level below and the top dividing grate is again filled with material.
This way it is assumed that a continuous operation of the shaft furnace is made possible.
In this known process only a low flow velocity of the combustion gas with respect to the material column they have to traverse can be attained, which leads to the fact that the materials spend a long time on each individual level.
Besides, the process is limited to the treatment of such materials wherein the combustion gases can also be used for the preheating. Finally, bridging and thereby caused irregularities in the flow are unavoidable, whereby especially the bridging in the burning area can have correspondingly disadvantageous effects due to flow irregularities on the chambers located above, particularly in what the even preheating of the material is concerned. Finally, it is quite difficult to completely discharge the load of the respective upper chamber and to completely fill the lower chamber by laterally extracting the subdivided grate from the shaft wall. The irregularities occuring during this operation cause additional irregularities in the heating of the material within the individual cross-sectional-levels of the shaft. Due to the fact that the combustion gas is introduced exclusively from the bottom, a very high shaft results, which again has to lead to a further reduction of the flow velocity of the combustion gas and to the thereto connected disadvantages.
It also has become known to treat porous additives made of swellable materials in the manner afore-described (German published specification No. 1 165 477). Thereby, the crushed material, such as clay or oil shale, is charged into chambers of a shaft arranged one on top of the other and each chamber is only partially filled. The chamber bottoms are made of lamellae rotatable around their longitudinal axis. Between the heap in the respective chamber and the bottom of the following chamber located above it, there is an intermediate clearance and the combustion gases produced by burners arranged laterally on the shaft walling are fed into these spaces. Thereby, a mechanical loosening of the heap is also performed in order to avoid bridging in the material due to the fact that the bottoms are rotatably driven and provided with downwardly directed teeth which reach almost to the next bottom.
To improve on the afore-mentioned state of the art, a further development has become known (German published specification No. 1 243 827) with burning chambers bilaterally arranged on a shaft, which are connected to the shaft interior through openings in the shaft walling, whereby the shaft interior is again subdivided into chambers by bottoms made of rotatable traps. Through an appropriate control of the bottom traps of the individual shaft chambers and through a charging device alternately covering one of the two burning chambers an alternate blasting of the respective material falling from one chamber into the other takes place, and due to that a desired turbulence of the material occurs with the result of a more even heating of the individual particles of material.
In the case of all these known processes the heating of the invidual material particles is very uneven which leads to the fact that a part of the material is overheated and another part thereof has not reached the required final temperature so that only an uneven thermal and/or chemical treatment of the material can be carried out.
In the case of the last-described processes and installations there is the further disadvantage of a relatively low energy efficiency in the use of the combustion gases, since these practically only graze the respective chamber bottoms and the surfaces of the heaps of material to be treated or flow around the material only during the short period of time of its free fall, so that it is necessary to provide a multitude of chambers corresponding to the desired temperature of the material to be heated.